1. Field of the Invention
The present invention relates to an ink jet ink, and an ink cartridge and an ink jet recording method using the ink.
2. Description of the Related Art
In an ink jet recording method, recording can be performed on various recording media. In addition, in order to realize more satisfactory image recording, for example, there are proposals concerning various inks depending on purposes, such as an ink suitable for recording an image with photographic image quality on glossy paper or the like and an ink suitable for recording a document on plain paper or the like. In recent years, the ink jet recording method has been utilized also in printing of, for example, a business document including a letter, a diagram, and the like using plain paper or the like as a recording medium, and an increase in utilization frequency thereof for such application is remarkable. Therefore, as for an ink suitable for recording a letter or a diagram on a recording medium such as plain paper, a pigment has more frequently been used as a coloring material for a color ink as well as a black ink.
Under such circumstances, various studies have been made on a monoazo pigment among organic pigments to be used for ink jet color inks because it has strong coloring power, provides an image excellent in color developability, and is also advantageous in terms of cost. In general, however, the monoazo pigment is particularly weak against heat as compared to other organic pigments. Hence, when the monoazo pigment is applied to an ink jet system in which an ink is ejected from a recording head by an action of thermal energy, ejection characteristics are liable to lower. For example, it is known that when C.I. Pigment Yellow 74 as a representative monoazo pigment is used, a pigment aggregate deposits in an ink flow path of a recording head, resulting in a reduction in ejection characteristics.
In order to deal with such problem, there is a proposal concerning an ink containing a monoazo pigment dispersed with a resin dispersant or a monoazo pigment capable of being dispersed in an ink without using any resin dispersant, and a substance for inhibiting aggregation of the pigment (see Japanese Patent Application Laid-Open No. 2006-225638 and Japanese Patent Application Laid-Open No. 2006-199744). According to the inventions described in Japanese Patent Application Laid-Open No. 2006-225638 and Japanese Patent Application Laid-Open No. 2006-199744, it is considered that reductions in ejection stability and storage stability of an ink are suppressed by enhancing the dispersibility of an aggregate even in an ink jet system utilizing thermal energy.